Process for the manufacture of most finely pulverized red phosphorus

ABSTRACT

Production of most finely pulverized red phosphorus, by subjecting an aqueous suspension of red phosphorus with a particle size of between about 50 and 100 microns, produced inside a ball mill from yellow phosphorus and water, to pulverization with agitation to obtain particles with a size between 1 and 20 microns, for example 10 microns, prior to filtering the suspension. The red phosphorus is produced using an apparatus wherein a preliminary tank, a preliminary agitator vessel and a ball mill having an agitator placed therein and filled with glass balls of between 1 and 2 mm. in diameter, are disposed ahead of the filter tank.

United States Patent {72] inventors FrltzMuller Knapsack near Cologne;

Karl-Heinz Stendenbaeh, Bruhl-Pingsdorf; 'Franz-Josei Dany, Lechenich;Dieter Steidl,

Sulzbnch/Taunus; Horst Heinrich Weizenkorn, Efferen near Cologne; WilliForst, Knapsack near Cologne, all of Germany [21] Appl. No. 860,275 [22]Filed Sept. 23, 1969 [45] Patented Dec. 21, 1971 [73] Assignee KnapsaekAktiengesellschait Eaefimzfiesnefisumy [32] Priority Oct. 3, 1968 [33]Germany [31] P 18 870.3

[54] PROCESS FOR THE MANUFACTURE OF MOST FINELY PULVERIZED REDPHOSPHORUS 2 Claims, 2 Drawing Figs.

[52] U.S.Cl 241/17, 241/25, 241/30 [51] lnt.Cl ..B02e 17/16, I B02c21/00 [50] Field oiSearch.....- 241/-17, 23, 25, 29, 23/223 [56]References Cited UNITED STATES PATENTS 3,493,182 2/1970 Szegvari 241/30X OTHER REFERENCES Mellor, J. W. A Comprehensive Treatise on Inorganicand Theoretical Chemistry, N.Y., Longmans, Green. Vol. VIII, 1928, page746, QD31M4.

Primary Examiner-Donald G. Kelly Attorney-Connolly and Hutz ABSTRACT:Production of most finely pulverized red phosphorus, by subjecting anaqueous suspension of red phosphorus with a particle size of betweenabout and microns, produced inside a ball mill from yellow phosphorusand water, to pulverization with agitation to obtain particles with asize between 1 and 20 microns, for example 10 microns, prior tofiltering the suspension. The red phosphorus is produced using anapparatus wherein a preliminary tank, a

preliminary agitator vessel and a ball mill having an agitator placedtherein and filled with glass balls of between 1 and 2 mm. in diameter,are disposed ahead of the filter tank.

PATENTEUmzvm A I 3628 739 SHEET 1 BF 2 I PATENTEUuzm Em 1628.739

SHEET 2 [IF 2 A suspension of about 25 weight percent red phosphorus inwater was pumped from a filter reservoir to the tank of a rotary filter;the filter tank was provided with a swingable conveyor belt. The filtercake having about 30 weight percent water therein, scraped off from thedrum of the rotary filter, was delivered to a trough conveyor maintainedunder nitrogen, and conveyed from there to a shelf drier maintainedunder nitrogen. Anhydrous red phosphorus having approximately thefollowing particle sizes was removed from the dri- 80% 40 microns 55% 25microns 30% microns.

The tank of the rotary filter was required to be freed after some hoursfrom red phosphorus which was found to have deposited therein.

Example 2: (Process of Invention) A suspension of about 35 weightpercent red phosphorus in water was pumped from a preliminary reservoirto a preliminary tank provided with an intense stirrer. Phosphorus whichprecipitated in the bottom portion of the preliminary tank wascontinually withdrawn through a slightly opened valve and recycled tothe preliminary reservoir. Overflow material coming from the preliminarytank was also recycled to the reservorr.

By means of a worm pump the suspension was conveyed from the preliminarytank to a ball mill equipped with an agitator, and forced to flowupwardly therethrough. The wetground suspension was then delivered to afilter reservoir basin and pumped from there to the tank of a rotaryfilter. The tank had a throttle valve disposed in its bottom portion,which effectively avoided the deposition of red phosphorus; an overflowwas used to maintain the depth of immersion of the filter drum constant.The filter cake scraped off contained about 30 percent adhering waterand was delivered to a paddle worm drier having nitrogen therein.Anhydrous red phosphorus was discharged therefrom. 97 to 100 percent ofthe phosphorus was found to have a particle size of 10 microns,depending on the quantity of suspension fed to the ball mill with theagitator therein.

Two exemplary representations of the present invention are showndiagrammatically in the accompanying drawings. Needless to say theinvention is in no way limited thereto. It can be modified in variousways without departing from its scope.

In the accompanying drawings,

FIG. I is an exemplary representation of the invention, and

FIG. 2 is a further exemplary representation of the invention.

As can be seen feedline 1 is used to supply and at least partially fillpreliminary tank 2, which has an agitator connected to it, with thephosphorus-water suspension. Pump 3 serves to convey the suspensionthrough line 4 to preliminary basin 6, which is equipped with anagitator 5 and connected to preliminary tank 2 by means of an overflowline 7 and a discharge pipe 8. Discharge pipe 8 has a discharge valve 9disposed therein which generally is but slightly opened. This is done tomake it possible for red phosphorus, which precipitates in the lowerportion of preliminary basin 6 and is no longer fluidized by agitator 5,to be returned to preliminary tank 2. The suspension travels frompreliminary basin. 6 through line 10 and is pumped by means of pump 11through line 12 to ball mill 14. Ball mill 14 is connnected to agitatorl3 and filled with glass balls 1 to 2 mm. in diameter (these are notshown in the drawing). The suspension coming from ball mill I4 flowsthrough a sieve placed above discharge pipe 15 and is conveyed throughpipe 16 to filter tank 17 having an agitator connected to it. By meansof a pump 18 and a line 19 the suspension is pumped to rotary filtertank 20, which has an overflow pipe 21 and a discharge pipe 22connecting tank 20 through line 23 to filter tank 17. Discharge pipe 22has a discharge valve 24 disposed in it, which generally is but slightlyopened.

The filter cake obtained in the rotary filter drum 25 is scraped off bymeans of a scraper 26 and delivered through down pipe 27 and rotarypiston pump 29 to drier 28. Drier 8 advantageously is a paddle wormdrier (e.g. a Solidaire-type drier) and is fed with steam of about l50C. Dry red phosphorus is removed from drier 28 through outlet opening30.

In accordance with the preferred representation shown in FIG. 2, line 19is arranged to be connected to a centrifugal filter 32 with plates 31.The centrifugal filter 32 is arranged to be driven by a motor 34 througha transmission 33. Positioned below centrifugal filter 32 is a filtrateoutlet 35. Line 36 is used to convey the filter cake from centrifugalfilter 32 to a buffer tank 38 connected to agitator 37. From buffer tank38, the filter cake is delivered through line 27 and a rotary pistonpump or worm pump 29 to drier 28. The rotary piston pump preferably is apump wherein each of the two rotary pistons and the pump casing arearranged to be spaced about 0.5 to 3 mm., preferably 1 mm. apart,leaving a gap therebetween.

We claim:

1. A process for the production of most finely pulverized red phosphoruswherein an aqueous suspension of red phosphorus coming from an agitatedfilter reservoir zone is pumped to a filter zone, and the resultingfilter cake, partially freed from water in the said filter zone, isintroduced into a drying zone and dried therein, which comprises pumpingan aqueous suspension of red phosphorus with a particle size of between50 and microns from an agitated preliminary reservoir zone, through anagitated preliminary zone to an agitating/grinding zone for reducing thesize of the particles of the red phosphorus down to 1-20 microns,pumping said suspension from said agitating/grinding zone to the saidfilter zone through the said agitated filter reservoir zone, recycling aportion of the suspension in the agitated preliminary zone to theagitated preliminary reservoir zone, and recycling a portion of thesuspension in the filter zone to the agitated filter reservoir zone.

2. The process of claim 1, wherein filter cake obtained by filtration ofthe said suspension is indirectly dried using steam of about C.

2. The process of claim 1, wherein filter cake obtained by filtration ofthe said suspension is indirectly dried using steam of about 150* C.